The Dobsonian mounted telescope is popular among amateur astronomers and telescope makers because of its simplicity. The Dobsonian mount is a form of an alt-azimuth mount adapted to carry a Newtonian reflector telescope. An alt-azimuth mount has an altitude axis on which the telescope pivots vertically and an azimuth axis on which the telescope rotates horizontally. In its simplest form, the typical Dobsonian mount consists of a saddle which allows the optical tube of the telescope to pivot in altitude, while the ground board is swivelled in azimuth. Traditional Dobsonian mounts are typically set on the ground for observing but a more compact tabletop version of the Dobsonian mount is also available.
The Dobsonian mount usually relies on the friction between the side bearings on the optical tube of the telescope and a frictional material on the saddle to hold the optical tube in place. If there is too much friction, the telescope is difficult to move to centre an object in the field of view. If there is too little friction, the telescope will not stay where it is positioned. This makes stabilizing the optical tube of the telescope difficult when using a Dobsonian mount, especially when accessories, such as a finderscope or an eyepiece, are added to the optical tube. As long as the amount of friction is at an appropriate level, and therefore stabilization of the optical tube is achieved, the telescope can remain in its desired position to view an object and maintain its position even when the mount is rotated to track an object as the Earth turns.
Various devices designed to assist in stabilizing telescopes on different types of mounts exist in the prior art. For example, Stock, U.S. Pat. No. 2,712,589 discloses a slidable weight to counter balance the weight of the telescope on an equatorial mount. Drauglis, U.S. Pat. No. 4,470,672 discloses a form of alt-azimuth mount wherein adjusters are used to regulate the tension between the cradle and the mounting ring to balance the telescope secured to the mounting ring. Baun et. al., WO 00/25168 discloses altitude and azimuth friction locks that both must be adjusted to inhibit movement of the telescope. Some Dobsonian mounts employ springs to aid in stabilization.
The devices for stabilizing a telescope currently available in the art are inconvenient to use because they do not provide a simple and user-friendly means to adjust the friction between the optical tube of a telescope and the Dobsonian mount.